Idle setting question.

[pete c]

Yeah, I know, there's a sticky thread on this topic. The answer is not there. I even asked this question in that thread, but, no answer yet.

My 93 mtx idles fine when first started. As it warms up and drops down to 800, it slowly drops lower, down to maybe 4-500. About the time the oil little flickers it shoots up to about 1800 and back down again, oscillating this way till it eventually stalls. I have replaced the Idle control valve or whatever it is called. Resetting the idle seems to help for a very short time, then it is back to the same old thing.

My question is, does having a shot AC compressor and burnt out AC clutch affect this? When setting the idle, I do turn on the AC, but all I get is a little bit of rattling from the clutch. There is not the usual compressor load. Also, does it matter if this is done with a cold or hot engine? I have done it cold. Guess I will try it with a hot engine next. Also, I do have some oil in the wells and the 60K valve service is way overdue. The car has 115K. I bought it with 89K and kinda doubt it ever got it's 60K , although it could have.

 

[Huntervf]

Sounds VERY similar to a problem a friend of mine had on a 93 MTX. His problem ended up being the fuel pressure regulator. You can to a quick test to see if this is the problem...just pop the hose off the regulator and cap the end with something to block off the vaccum (but make sure it's something that won't get sucked into the intake). Your car will run pig rich but if your idle problem goes away then you'll know what to replace.

 

[sdpatt]

The throttle position sensor also has a role in the idle speed, but the condition on your engine still sounds like a faulty IAC valve.

 

[stevemainian]

I have a similar problem on my ATX, except mine will only do what yours did when warm.

My rpms will bounce around, then just stall. Obviously its not the IAB because if it was, i would have a problem starting it, starts up fine.

I think it may be the cps/cks but its hard to prove without doing a bit of work.